This Center grant requests funding for seven core facilities to support a broadly-based research program in the study of mental retardation and developmental disabilities. The seven core facilities are: Administrative, Multimedia, Imaging, Cellular Neuroscience, Gene Manipulation, Molecular Genetics, and Cell Sorter. The Cores have undergone major development and support the research of 65 investigators. The research is in two programmatic areas, i.e., Genetics and Neuroscience. In Genetics, directed by Dr. Louis Kunkel, there are seven major research efforts, which include the molecular genetics of neuromuscular disease, somatic cell genetics, gene therapy and stem cell research. In Neuroscience, there are three major programs, i.e., Basic Neuroscience, Clinical Neuroscience/Behavior and Developmental Biology. The Basic Neuroscience Program, directed by Dr. Michael Greenberg, consists of 27 investigators whose research efforts span a broad spectrum of interdigitated research in molecular, cellular, and systems neurobiology, with a strong overall emphasis on development and developmental neurological disorders. A research project in Basic Neuroscience, proposed in this application as a "New Program", addresses "Signaling Mechanisms Mediating Axon Guidance Effects of Semaphorin 3A" (Zhigang He, Ph.D.). A second major program in Neuroscience, i.e., Clinical Neuroscience/Behavior, directed by the Center Director, includes 27 investigators whose research efforts include such areas as neonatal brain injury, behavioral development, learning disturbances, structural/functional brain imaging, and molecular genetics of human brain development. These areas of clinical research interdigitate with the basic research in the MRRC. A third exciting program in Neuroscience, i.e., Developmental Biology, directed by Dr. Merton Bernfield, addresses such areas as mechanisms of embryonic development, serpin biology and regulation of pregnancy duration. The multidisciplinary approaches to the research of this MRRC include the various basic science disciplines within Genetics and Neuroscience, and the clinical science fields of Neurology, Pediatrics, Neonatology, Infectious Disease, Endocrinology, Metabolism, Genetics, Cardiology, Neurosurgery, Neuropathology, Ophthalmology, Psychiatry, and Psychology. The basic science programs are housed in over 70,000 square feet of the Enders Pediatric Research Building. The clinical research programs are centered in the adjacent Children?s Hospital.